Method of reclaiming turnings of readily-oxidizable metals.



l. COULSUN.

METHOD OF RECLAIMING TURNINGS OF READILY OXIDZABLE METALS.

APPLICATION FILED SEP?, 22. 1915.

1,292,582, ,muted Jan. 28,1919.

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'To all :whom tmc concern.' Y

Be it hnownt at'I, JoHN.ConLsoNa suhieot of the King of Great Britain, and a resident of'Wilkinshur in the county of ennsylvania, have invented a new and useful Improvement in Methods of Reclaiming .IT s of Readily-Oxidizable Metals, of which the following is a specification.

My inventlonrelates to methods ofreclaiming and melting into homogeneous metallic form the turmngs and borings which result from machinin operations upon readily oxidizablemeta s and alloys of the aluminum class, and it Ahas special reference to methods of reclaiming borings and turnin s of magnalium.

.he object of my inventionY isto provide a simple and commerciallypracticable process of the above indicated character whereby turnings of aluminum, magnalum and other readily oxidizable metals and alloys A may hemelted into solid metallic form with a minimum amount of loss.

in the accompanying drawing, Figure l is a vertical sectional view illustrating one .form of apparatus suitable for carrying out my invention, and Fig. 2 is a vertical sectional viewof a cruclble adapted for-use in practising a modied form of my invention. i

My present invention finds special commercial utility in the treatment of borings and turnings of the alloy magnalium,V and process will therefore he described spec` cally with relation to this substance without, however, limiting my invention thereto. Magnalium, on account of its lightness, high tensile strength and other desirable physical characteristics is very largely used in the manufacture of castings and other machine parts, and the operations performed upon such castings result in the production of large amounts of more or less finely divided turnings,`borings and otherjforms of scrap. This scrap metal cannot be melted down by ordinary methods on account of the very great rapidity with which the material is oxldiz'ed. 'It is found that magnalium oxidizes even more rapidly and violently than metallic aluminum itself. In melting magnalium scrap, it hastherefore been customary, up to the present time, to make` use of strong fluxes, such as the chlorids and iuorids of the .alkali and al- 'closed b 'Anuman-nea september z2, 1915. semina. 51,948.

kaline earth metals, for the purpose of dis'- solring the oxid scale which covers the particles of metal and, by the production of gas., to mechanically a itate the molten metal and promote its di u'sion. Cryolite, for enample, is very commonly used' as a hun under these circumstances. y

.The use of cryolite as a 'hun is obiectiom .able on account of the vigor with which it attacks silicon or 'clbles of iron or ot er metal cannot be used aphite cruel-bles. Cruon account of the dissolving action of kmolten. magnalium, and it is therefore highly desirable to avoid the use of strong fluxes and,

at the same time, to keep the melting losses as low as possible.

According to one modification'of my present invention, I melt metallic turnings of the above mentioned kinds in the'presence of an inert or reducing gas, which may conveniently be hydrogen. The gas should be specification of Letter rami-t.'l Patented Jan. 28,1919.

applied'to" the metal in such maner as to pass through it during the heating process, which may be accomplished, for example, by means of the apparatus shown in Fig. 1 of the drawing. This apparatus consists of a circular casing l divided into u per and lower chambers 2` and 3 connecte by a vertical passage 4. The ends of the Casin l are inscrew caps '5 'and ,6. deans are provide rfor heating the casing throughout its length, suchv means, as shown, comprising an electrical resistance coil 'l embedded in the walls ofthe casin terminals 8 to which eectric energy may be supplied from -any suitable source. ny other convenient heating means may of course he substituted for the electric heating coil 7 andthe casing may he made of any suitable material.

A crucible 9 is received in the upper chamher 2 ofthe casing l and is provided with a perforated bottom 10 disposeddirectly above the vertical passage 4. A crucible 11 is disposed in the lower chamber 3 of the casing 1 for the purpose of receiving molten metal. A pipe 12 communicates with the chamber 2 through'the cap 5 and another pipe 13 com-- and provided with Y .In the operation of this form of device, the

metallicturnin to be melted are placed in the crucible 9, t e casing is tightly closed and hydrogen or other suitable inert or reducing gas is introduced under pressure through the pipe 12. Since the gas outlet pipe 13 is of smaller diameter than the plpe 12, a considerable degree of pressure is maintained at all times in the crucible 1,1. The

as should be passed through the apparatus or several minutes in order to wash it thoroughly free from oxygen, and heat is then applied by energizing the coil 7 to raise the temperature within` the treating vessel to about 900"Y C. I fmd it convenient to apply the gas'from above and unde'r such pressure that the globules of molten metal produced by lthe heat treatment are forced through the perforations in the plate on which the turnings. rest, and I iind that this method produces la very satisfactory recovery of magnalium. v

It is very desirable that the metal 'particles be cleansed as thoroughly 4ias possible before they are melted, andthe-cleansingtreatment may convenlently.' beA combined with the addition of small amounts of weak fiuxing agents which arevsometimes desirable. vSince the metal is usuallycontami-l nated with oil or grease, a preliminary washing with benzin or other solvent isy desirable,

' and the metal may then be boiled lfor a 'few minutes in a weak-solution'of afluxing agent,

which 'solution may bea 4% solution of sodium chlorid. This 'boiling treatment not only .cleanses the metal to a 'considerable 'extent, but replaces the air entangled 'by the metal, while` the 'small amount of sodium chlorid which adheres tothe metal serves the `purpose of a vweak ux during-the subsequent melting operation. y

The cleansed metal, treated in the manner `just described, may either be 'subjected to the foregoing heat treatment in the presence ogas or it may ,bemelted in an open crucible according to the following method.' An

ordinaryY graph-ite or silicon crucible, suchA as is shown at 15in Fig. 2 of the drawing, is

heated to a temperature of about 900 C.,

andthe metallic turnings,previously washed in .benzin and boiled in a weak salt solution, f are fed into the hot crucible -while they are damp. The introduction of the turnings is accompanied by mechanical stirring,

v the molten pool, which is 4agitated as before alf-ter each addition, and the molten metal is rtapped ofi 'from time to time from the lbot- -u-tesaiiterrth last pnddling operation, which gives the oXids which may be present time to rise to the surface where they float as a slag, while the 'clean metal may be poured from lbeneath. The dross remaining inthe crucible after Apouring lcontains seme good 'metal which may be separated from the oxid by adding 'a small quantity 'of calcium-chlorid and stirring vigorously.

v"During the pnd'dling ltprccess -described above, the heat may' sometimes rise suiii- :ciently tov ignitel the metal in `*the crucible.

In such case, QI find that'the may ie checked immediately "by sprinkling" into the crucible a Ismal-l lqlfrant'ity ofpowdered cryolite. Inforder to Vavoid ignition of Ythe vchargeduring pouring, I prefer 'to tap A-oii 1 the molten l`metal from the 'bottom vof the crucible.

The 'metal obtained vby the foregoingv methods always contains a 'smail vamount 'of metallic oxids which render the product in# "feriorr tothe 4original -magnalium -or other metal fromwhic'h the turnings were made. In order to improve the `quality 'of the final product by removing 'such entangled oxids, -I prefer to'add to the contents of "the 'cru- Y cible, lin the course of the paddling process,

a small amount or a tie-'omd'zing agent.

"Such de-oxidizing :agent may be 'any one of a number off-substances, but 'I 4prez'c'er to employ, for this purpose, either -metallic calcium or calcium-aluminum silicid, which need be'added only 'the 'proportion vof 11;% to 1J% of the charge of the crucible.

The several process 'steps which I have described may be combined in any convenient order or number as the requirements of special operations may make necessary or as the operator may desire. It is to be understood that -my invention comprehends Aall such variations 'and that, in general, no limitations are 'to 'beim'posed -upon my invention except such as 'are indicated in the appended claims.

I claim 'as my invention:

l.. The Ymethod of melting subdivided bodies of readily oxidizable metal that comprises boiling 'the subdivided vmetal in a solution of a fluxing agent, Amelting a solid mass of the same metal in a crucible, adding to the molten pool successive lsmall increments ofthe subdivided metal, while still moistened with the said solution, and stirring the pool after each increment is added.

2. The method Aof melting subdivided bodies of readily oxidizable metal that comprises boiling the subdivided metal in a solution of sodium chlorid, melting a solid mass of the same metal in a crucible, adding to the molten pool successive small increments 5 of the subdivided metal, While still moistened with .the said solution, and stirring the pool after each increment is added.

3. The method of melting subdivided bodies of readily oxidizable metal that com- 10 prises combining successive increments of the metal while excluding air, separating the molten metal from the supernatant slag,

heating the said slag with an alkaline earth metal chlorid and removing the molten metal which separates from the slag.

4. The method of melting subdivided bodies of readily oxidizable metal that comprises combining successive increments of the metal While excluding vair and adding a small amountvof a de-oxidizing agent containing calcium-aluminnm silicid.

In testimony whereof, I have hereunto subscribed my name this 21st day of Sept., 1915."

JOHN COULSON. 

